C5 to c16 aliphatic alcohols used as defoaming agents in zinc oxide-resin dispersions

ABSTRACT

A LIGHT SENSITIVE MATERIAL FOR ELECTROPHOTOGRAPHY COMPRISING A BASE MATERIAL AND A LIGHT SENSITIVE LAYER PROVIDED THEREON, IN WHICH THE LIGHT SENSITIVE LAYER COMPRISES A WATER SOLUBLE RESIN AND AN ALIPHATIC ALCOHOL HAVING A DEFOAMING CHARACTERISTIC AND WHICH HAS THE FUNCTION OF IMPROVING THE ELECTROPHOTOGRAPHIC CHARACTERISTICS.

June 1972 NARIO YAMAGUCHI ETAL 3,671,235

C 3 TO C ALIPHATIC ALCOHOLS USED AS DEFOAMING AGENTS IN ZINC OXIDE-RESIN DISPERSIONS Filed Dec. 5, 1968 A. 3 x3 Fcztmzmm m m m ALIPHATIC ALCOHOL WEIGHT US. Cl. 961.8 3 Claims ABSTRACT OF THE DISCLOSURE A light sensitive material for electrophotography comprising a base material and a light sensitive layer provided thereon, in which the light sensitive layer comprises a water soluble resin and an aliphatic alcohol having a defoaming characteristic and which has the function of improving the electrophotographic characteristics.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to an improvement in light sensitive materials for electrophotography comprising a base material and a light sensitive layer provided thereon, in which the light sensitive layer comprises a photoconductive material, a water soluble resinous binder and an aliphatic alcohol having both a defoaming characteristic and a function of improving electrophotographic characteristics.

(2) Description of the prior art In the conventional methods of producing the light sensitive layer on the copy material for electrophotography there are primarily used oxidized metallic materials such as titanium oxide as photoconductive materials and resins of high electric resistance characteristics generally soluble in organic solvents as resinous binders for binding the photoconductive materials to the base materials. However, because of the photoconductive material and the resinous binder dissolved in the organic solvent for the formation of the light sensitive layer, considerable added investment is required for providing safety devices in order to prevent fire, explosion and health hazards from the organic solvents or their vapors.

To avoid the special equipment used to overcome the above-mentioned hazards, various water soluble (or water dispersi-ble) resinous binders have heretofore been proposed, but none of the proposed binders has successfully been put into practical use because they cause deterioration of the electrostatic characteristics of the printed electrophotographic materials such as low charge potential during corona discharge and considerable dark attenuation or decay of electric potential when the copy material has been left in the dark after charging.

SUMMARY OF THE INVENTION This invention provides, in the copy materials for electrophotography having a base material and a light sensitive layer thereon, a copy material for electrophotography in which the light sensitive layer is formed by a water solution comprising an aliphatic alcohol of a high defoaming characteristic and also having a function to improve the electrostatic characteristics of the resultant copy print.

To further elucidate this invention, there is employed a water soluble resin as a resinous binder for the light sensitive layer in combination with an aliphatic alcohol United States Patent O ice as a defoaming and characteristic-improving agent to prevent deterioration of the elcctrophotographic characteristics of the sensitive layer which would otherwise occur. Normally, when a water soluble resin or a water dispersed resin, such as an emulsion, is mixed with zinc oxide powder and the mixture is mechanically dispersed, foaming inevitably occurs and thus considerably hampers the electrophotographic characteristics of the light sensitive layer. On the other hand, there is scarcely any defoaming agent known in the art which eliminates the foams and concurrently prevents deterioration of the electrophotographic characteristics of the light sensitive layer. The known interface activators having defoaming functions seem to hamper, without exception, the characteristics of the light sensitive layer by lowering, for example, the charging potential, or the light sensitivity by preventing absorption of the sensitizer to the photoconductive material. A silicone defoaming agent is no exception for the same reasons as those given for the interface activators.

Thus, by studying countless examples of defoaming agents, the inventors observed that an aliphatic alcohol not only has the required defoaming characteristics, but it is considerably effective in improving sensitivity, charging characteristics, dark attenuation and weathering characteristics of the light sensitive layer of the electrophotographic material when used as a layer forming material in combination with resinous binders.

The aliphatic alcohols usable for this invention as the defoaming and characteristic-improving agent include the following:

n-Amyl-alcohol CH (CH CH OH Iso-amyl-alcohol (CH CHCH 'CH OH Tert-amyl-alcohol CH CH COH(CH Sec-amyl-alcohol CH (CH CHO'HCH Diethyl-carbinol (CH CH -CHOH Activated amyl-alcohol CH CH CH(CH )CH OH n-Hexyl-alcohol CH (*CH CH OH n-Heptyl-alcohol CH (CH CH OH n-Octyl-alcohol CH ('CH CH OH Secp-octyl-alcohol CH (CH CHOHCH n-Nonyl-alcohol CH (CH CH OH n-Decyl-alcohol CH (CH CH OH n-Undecyl-alcohol CH (CH CH OH Lauryl-alcohol CH (CH CH OH Myristyl-alcohol CH (CH ICH OH Cetyl-alcohol CH (CH CH OH of which n-hexylalcohol, n-octylalcohol, n-nonylalcohol and laurylalcohol are found suitable for the embodiment of the present invention.

The water-soluble resins for binding which may be used in the embodiments of this invention include melamine-formaldehyde resin, urea-formaldehyde resin, water-soluble alkyd resin, water-soluble acrylic resin, water-soluble vinyl acetate copolymer resin, Water dispersible synthetic rubber, resin emulsified to O/W type with an emulsifying agent and resin modified with basic substance, all of which may be used in the form of a water solution or a water dispersion.

The light sensitive material according to the present invention is produced by applying on to the base material and then drying the light sensitive layer forming water solution consisting of any of said water-soluble resins and aliphatic alcohol with 5 to 16 carbon atoms added thereto at the ratio of at least 0.2% by weight thereof as a defoaming and characteristic-improving agent, dissolved or dispersed in water together with a photoconductive material or with a combination of a photoconductive material and a sensitizer.

Now, in reference to the attached figure, there will be described below the relation between the amount of aliphatic alcohol added to the light sensitive layer and the characteristics of the light sensitive layer of the light sensitive material, when n-octylalcohol and vinyl acetatecrotonic acid copolymer are used as a defoaming and characteristicimproving agent and a binding resin respectively. The figure shows the characteristic curve of electrophotography in which the abscissa represents the amount of aliphatic alcohol added to the light sensitive layer (in percentage in weight to the solid weight of the resin) and the ordinates represent the dark attenuation factor (or dark decay ratio) and the degree of sensitivity. Curves 1 and 2 show the degrees of sensitivity and the dark attenuation factors respectively. It is clear from these curves how such characteristics change depending upon the added amount of aliphatic alcohol. The dark attenuation factors indicated herein have been obtained in accordance with the following formula in which V represents the electric potential of the light sensitive layer at the point 5 seconds after the suspension of the application of the electric charge by corona discharge for 30 seconds in an ordinary manner and V represents the electric potential of the light sensitive layer as it has been left in the dark for 30 seconds after the suspension of the corona discharge.

Formula for obtaining the dark attenuation factor 25?) X100=Dark attenuation factor (percent) The degree of sensitivity is indicated in terms of the amount of illumination (lux-sec.) required to reduce the electric potential V of the light sensitive layer down to of V when such light sensitive layer with the potential of V is illuminated.

It is noted from the figure that as the amount of aliphatic alcohol increases, the dark attenuation factor becomes lower with an attendant improvement in the degree of sensitivity. This means that because of such characteristics, a clear reproduction image having a satisfactory contrast may be formed on the light sensitive material according to the present invention. Furthermore, the results of the similar characterization tests using combinations of said resins and other aliphatic alcohol than n-octyl alcohol show substantially the same trend as shown by curves 1 and 2 of FIG. 1.

BRIEF DESCRIPTION OF THE DRAWING The figure indicates the characteristic curves of electrophotography showing the relation between the amount of aliphatic alcohol as a defoaming and characteristicimproving agent of this invention and the dark attenuation factor (or dark decay ratio) and the degree of sensitivity of the electrophotographic characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Photoconductive zinc oxide g- 100 Goseran (a trade name of a product manufactured by Japan Synthetic Chemical Co., Ltd.) -g 20 n-Octyl alcohol 0.2 Sensitizer (0.5% methanol solution of rose bengal and fluorescein) -..cc 1 Tap water ....g 180 1 Solid Weight.

4 an electrophotographic light sensitive material was finally obtained.

For comparison purposes, another light sensitive material was prepared by similarly applying on to the base material, then drying and conditioning the same light sensitive layer forming solution as above, which however, does not include, n-octyl alcohol. Electric charge was applied to the light sensitive materials thus prepared and the saturation potentials, dark attenuation factors and degrees of sensitivity were measured. The results are shown in Table 1.

density was formed on the light sensitive material of this invention as compared with the control material when such light sensitive materials were employed in the actual reproduction process. In addition, the copying speed of the material according to this invention was found faster than that of the control product, because of the higher sensitivity of the former.

Example 2.

An electrophotographic light sensitive material was similarly prepared by employing a light sensitive layer forming solution which has the same composition as the one used in Example 1 except that in this Example 2 n-octyl alcohol was replaced with 0.5 g. of n-hexyl alcohol. The performance of the light sensitive material thus prepared was found to be substantially similar to that of the light sensitive material according to this invention as described in Example 1. It was recognized that the material of this example showed particularly good performance in the reproduction process carried out in a high humidity atmosphere (75% RH).

Example 3 Example 4 Photoconductive zinc oxide g Water-soluble acrylic resin (trade name S4005 manufactured and sold by Toa Synthetic Chemical Co., Ltd.) g 1 20 Lauryl alcohol (reagent of 1st class) g..- 0.1 Sensitizer (the same as the one in Example 1) cc 1 Tap water g 100 1 Solid weight.

A light sensitive layer forming solution with the above composition was treated in the same manner as in Exampie 1 to obtain an electrophotographic light sensitive material. Por comparison purposes, another electrophotographic light sensitive material was prepared by employing a light sensitive layer forming solution which is otherwise the same as the aforementioned solution but only lacks lauryl alcohol. The electrophotographic characteristics of such light sensitive materials were measured and the results are shown in Table 2 below.

TABLE 2 Dark Foaming Saturaattenucharactertion p ation Light sensitive istics of tential factor, Sensitivity material binding resin (V/ percent (Lux. sec.)

Material of this None 28 14 300 invention.

Control material Remarkable 26 19 360 It was further noted that a clearer reproduction image was formed on the light sensitive material of this invention as compared with the control in theactual reproduc- An electrophotographic light sensitive material was prepared by treating a light sensitive layer forming solution with the above composition in the same manner described in Example 1. For comparison purposes, another electrophotographic light sensitive material was prepared by similarly treating a light sensitive layer forming solution which is the same with the said solution except that the former lacks n-octyl alcohol. Then, the saturation potentials, dark attenuation factors and degrees of sensitivity of each of such materials were measured. The results obtained were substantially similar to those shown in Table 2. Also, the same kinds of diiferences as in Example 4 were noted when the materials were utilized in the actual reproduction process.

What is claimed is:

1. An electrophotographic copying material comprising an electroconductive support coated with a photoconductive layer consisting essentially of a mixture of zinc oxide, a water soluble or water dispersible resinous binder, and an antifoaming agent consisting of more than 0.2% by weight, relative to the weight of the resinous binder, of an alkanol having 5 to 16 carbon atoms.

2. An electrophotographic copying material as claimed in claim 1, in which said alkanol is selected from the group consisting of n-hexyl alcohol, n-octyl alcohol, nnonyl alcohol and lauryl alcohol.

3. An electrophotographic copying material as claimed in claim 1 in which the amount of the anti-foaming agent contained in said layer is in the range of 0.2 to 3.0% by weight based on the weight of the resinous binder.

References Cited UNITED STATES PATENTS 2,827,392 3/1958 Seats 252358 X 2,903,377 9/1959 Saulnier 252358 X 2,993,787 7/1961 Sugarman 961.8 3,146,158 8/1964 Donnelly 252-321 X 3,261,709 7/ 1966 Schulman 961.8 X

FOREIGN PATENTS 630,362 10/1963 Belgium 96--1.8

GEORGE F. LESMES, Primary Examiner R. E. MARTIN, Assistant Examiner US. Cl. X.R. 

